1. Field of the Invention
The present invention relates to a housing or chamber for a fan for moving air, pump for inducing fluid flow or torque generator, which is responsive to fluid flow such as a turbine. In particular it is directed to providing an improved housing for such apparatus to improve the efficiency of such devices.
2. Description of the Related Art
Centrifugal fans, blowers, pumps turbines and the like represent approximately half of the world's fan, pump and turbine production each year. As fans or pumps, they are used to produce higher pressure and less flow than axial impellers and fans. They are used extensively where these parameters must be satisfied. They have also been used advantageously where installation limitations might not permit an axial fan to be used.
For example, applications such as domestic exhaust fans require greater flow with a relatively low pressure difference. Such an application would normally be satisfied by an axial type of fan. However, in many cases, a centrifugal fan is used to turn the flow path at right angles so that it can fit into a roof or wall cavity. An axial fan will not fit into the cavity and maintain efficiency. In another example, the exhaust ducting in many buildings is only 3 or 4 inches in diameter. It is impractical to fit an effective high-output axial fan to such a small duct.
While centrifugal fans have been used for a long time, little attention has been given to the design of the housing in which the rotor is retained. Where issues of efficiency and noise are investigated, the designer's attention is given primarily to the impeller. Historically, such housings have not been optimized for: 1. fluid flow drag reduction; 2. noise reduction; 3. adjustment of the pressure/flow relationship. Additionally, the housings of typical centrifugal fans, blowers, pumps turbines and the like cause the incoming fluid to turn sharply before leaving the housing. Such shapes are detrimental to efficient performance of the device overall, often introducing significant turbulence.
In the previous disclosure of the applicant for a Fluid Flow Controller as published in W003056228, the applicant has noted the benefits that can be obtained by allowing fluid to flow in the manner followed in Nature.